1. Field of the Invention
The present invention relates to an image sensor module incorporated in a device having an image capturing function, such as a digital camera, mobile phone or camera-integrated watch. The present invention also relates to a method of making such an image sensor module.
2. Description of the Related Art
Conventionally, an image capturing device such as a digital camera incorporates an image sensor module for converting optical image data of an object into electric signals. An example of prior art image sensor module is illustrated in FIG. 8. In the prior art image sensor module 200 shown in the figure, an image sensor chip 1 and internal terminals Ta electrically connected to the image sensor chip 1 are enclosed in a package 209. The image sensor chip 1 is formed, at the upper surface thereof, with a light receiving portion 11. When the light receiving portion 11 receives light, image signals with output levels corresponding to the received amount of light are generated by photoelectric conversion elements and outputted from electrode pads. The package 209, which protects the image sensor chip 1, is formed with an opening which is closed with a cover glass 291. Each of the internal terminals Ta is connected to a corresponding external terminal Tb projecting outward of the package 209, thereby providing a connection terminal T′.
As shown in FIG. 9, the image sensor module 200 is used in combination with a lens 103 for converging light reflected by an object onto the image receiving portion 11. Specifically, for using the image sensor module 200, a lens mount 204 for supporting the lens 103 is prepared. As shown in the figure, the lens mount 204 is so disposed as to cover the image sensor module 200.
In the above prior art, a lens mount 204 need be separately prepared from the image sensor module 200. Therefore, the number of parts and the process steps for the manufacturing are increased as a whole, which results in a high manufacturing cost. Further, since the lens mount 204 need be larger than the image sensor module 200, the entire size is inevitably increased.
FIG. 10 illustrates another prior art image sensor module disclosed in JP-A-10-41492. As shown in the figure, the image sensor module 100 includes an image sensor chip 1 and a lens 103 which are supported by a frame 104.
The image sensor chip 1 is mounted on an upper surface of a substrate 2. The substrate 2 has a lower surface formed with connection terminals T, which are electrically connected to the image sensor chip 1. The frame 104 includes a chip case portion 104a for covering the image sensor chip 1 and a lens mount portion 104b located above the chip case portion 104a. The frame 104 is formed of a resin so that the chip case portion 104a and the lens mount portion 104b are integral with each other to provide a generally cylindrical configuration as a whole. The chip case portion 104a has a flat lower end surface to which the substrate 2 is attached.
The lens mount portion 104b is internally formed with a stepped portion 140 upon which the lens 103 is placed. Thus, the inner space of the frame 104 is sealed by the substrate 1 and the lens 103. Use is made of a lens cap 108 for holding the lens 103 in place relative to the stepped portion 140 so that the lens 103 does not come out of the lens mount portion 104b. More specifically, the lens cap 108 is fitted outwardly to the lens mount portion 104b from above, so that the peripheral portion of the lens 103 is sandwiched between a thick wall portion 108a of the lens cap 108 and the stepped portion 140. At this time, the lens 103 and the image sensor chip 1 are so arranged that the optical axis of the lens 103 is perpendicular to the light receiving portion 11. Further, the distance between the lens 103 and the image sensor chip 1 is so set that parallel light entering the lens portion 103 forms a proper image on the light receiving portion 11.
An image sensor module often includes a diaphragm for increasing the depth of field so that the precise focusing is unnecessary. In this image sensor module 100, the lens cap 108 is formed with an aperture 107 as a diaphragm.
Unlike the image sensor module 200, the image sensor module 100 incorporates the lens 103, so that any external lens or lens support is not necessary. Further, since the lens 103 is fixed to the frame 104 just by fitting the lens cap 108 to the frame 104, the module can be assembled at a relatively low cost. Moreover, unlike the image sensor module 200, the image sensor chip 1 is used as it is (i.e., without being packaged). Therefore, the image sensor module 100 can be made smaller in entire area surface than the image sensor module 200.
However, since the image sensor module 100 utilizes the lens cap 108, the overall cost of the structural parts will be high accordingly.
Further, recently, there is a demand for thickness reduction of an image sensor module for incorporation in a thin device such as a mobile phone or a watch for example. However, due to the additional thickness of the lens cap 108, the image sensor module 100 is not a suitable unit to provide a device that should be compact.